Variable Focus Liquid Filled Lens Apparatus

ABSTRACT

A variable focus optical apparatus including a rigid, curved, transparent optical component; two transparent, distensible membranes attached to a periphery of the rigid optical component to define two cavities, a first cavity between the rigid optical component and a first membrane and a second cavity between the first membrane and a second membrane; and a variable amount of fluid filling each of the cavities, and a reservoir containing additional fluid and in fluid communication with the cavity, wherein the reservoir is configured to provide injection of fluid into the cavity or withdrawal of fluid out of the cavity in response to a force or an impulse.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of and claims priority to U.S.application Ser. No. 12/370,938, filed Feb. 13, 2009, the disclosure ofwhich is incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of variable focus lenses, andmore particularly to consumer ophthalmic lenses that are at least inpart fluid- or liquid-filled.

2. Background Art

It is known that the ability of the human eye to accommodate, i.e., toalter the focal length of the natural lens in the eye, is graduallydiminished with increased age. Accommodation in human beings is reducedto 3D (diopters) or less at an age range of 35-45 years. At that point,reading glasses or some other form of near vision correction becomesnecessary for the human eye to be able to bring near objects (such aslines of text in a book or a magazine) to focus. With further aging,accommodation drops below 2D, and at that point visual correction whenworking on a computer or when performing some visual task atintermediate distances is needed.

For best results and for best visual comfort, it is necessary to bringeach eye to focus on the same viewing target, e.g., a computer screen. Alarge segment of population requires a different visual correction foreach eye. These people, known as anisometropes, require different visualcorrection for each eye in order to achieve maximum visual comfort whilereading or working on a computer. It is known that, if each of the twoeyes of anisometropes is not brought to focus at the same viewing plane,the resulting anisometropic image blur causes a loss of stereopsis(depth perception). Loss of stereopsis is one of the best indications ofloss of binocular function. Loss of binocularity at the reading planemay cause a drop in reading speed and rate of comprehension, and mayhasten the onset of fatigue upon sustained reading or working on acomputer. Reading glasses fitted with individually adjustable liquidlenses are therefore uniquely suited for the visual need of individualswith loss of binocular function.

Variable focus lenses can take the form of a volume of liquid enclosedbetween flexible, transparent sheets. Typically, two such sheets, oneforming the lens front surface and one forming the lens back surface,are attached to one another at their edges, either directly or to acarrier between the sheets, to form a sealed chamber containing thefluid. Both sheets can be flexible, or one can be flexible and onerigid. Fluid can be introduced into or removed from the chamber to varyits volume, and, as the volume of liquid changes, so does the curvatureof the sheet(s), and thus the power of the lens. Liquid lenses are,therefore, especially well suited for use in reading glasses, that is,eye glasses used by presbyopes for reading.

Variable focus liquid lenses have been known at least since 1958 (see,e.g., U.S. Pat. No. 2,836,101, to de Swart). More recent examples may befound in Tang et al, “Dynamically Reconfigurable Liquid Core LiquidCladding Lens in a Microfluidic Channel”, LAB ON A CHIP, Vol. 8; No. 3,pp. 395-401 (2008), and in International Patent Application PublicationNo. WO 2008/063442, entitled “Liquid Lenses with Polycyclic Alkanes”.These liquid lenses are typically directed towards photonics, digitalphone and camera technology, and microelectronics.

Liquid lenses have also been proposed for consumer ophthalmicapplications. See for example, U.S. Pat. Nos. 5,684,637 and No.6,715,876 to Floyd, and U.S. Pat. No. 7,085,065, to Silver. Thesereferences teach pumping of liquid in or out the lens chamber to changethe curvature of an elastic membrane surface, thus tuning the focus ofthe liquid lens. For example, U.S. Pat. No. 7,085,065, entitled“Variable Focus Optical Apparatus”, teaches a variable focus lens formedfrom a fluid envelope comprising two sheets, at least one of which isflexible. The flexible sheet is retained in place between two rings,which are directly secured together, such as by adhesive, ultrasonicwelding or any similar process, and the other, rigid sheet may bedirectly secured to one of the rings. A hole is drilled through theassembled lens to allow the cavity between the flexible membrane and therigid sheet to be filled with transparent fluid.

Liquid lenses have many advantages, including a wide dynamic range, theability to provide adaptive correction, robustness and low cost.However, in all cases, the advantages of liquid lenses must be balancedagainst its disadvantages, such as limitations in aperture size,possibility of leakage and inconsistency in performance. In particular,Silver has disclosed several improvements and embodiments directedtowards effective containment of the fluid in the liquid lens to be usedin ophthalmic applications, although not limited to them (e.g., U.S.Pat. No. 6,618,208 to Silver, and references therein). Power adjustmentin liquid lenses has been effected by injecting additional fluid into alens cavity, by electrowetting, by application of ultrasonic impulse andby utilizing swelling forces in a cross linked polymer upon introductionof a swelling agent such as water.

Commercialization of liquid lenses is expected to occur in the nearfuture, provided that some of the limitations noted above can beremedied. Even so, the structure of prior art liquid lenses is bulky andnot aesthetically suitable for consumers, who desire spectacles havingthinner lenses and spectacles without bulky frames. For the lenses thatoperate by injection or pumping of liquid into the body of the lens, acomplicated control system is usually needed, making such lenses bulky,expensive and sensitive to vibration.

In addition, to date, none of the prior art liquid lenses provides theconsumer with the ability to introduce the liquid into or remove it fromthe lens chamber so as to himself change its volume in order to vary thepower of the lens.

BRIEF SUMMARY

In accordance with the objects of the invention, a liquid-filled lensfor consumer, ophthalmic applications is provided. The lens has a frontmember that is rigid provided by an optic made of glass or plastic, aback surface comprising a flexible membrane stretched over the edge ofthe rigid optic, and a fluid filling the cavity formed between the frontoptic and the flexible membrane. The liquid-filled lens may comprise oneor more liquid filled cavities, contained by a corresponding number ofmembranes. Each liquid filled cavity is sealed, and is under a positivepressure in order to maintain the membrane in a stretched state. Thefront optic may have an aspheric surface geometry and may have ameniscus shape.

In certain embodiments, the invention provides a variable focus opticalapparatus comprising a rigid, curved, transparent optical component, atleast one transparent, distensible membrane attached to a periphery ofthe rigid optical component to define a cavity therebetween, a variableamount of fluid filling the cavity, and a reservoir containingadditional fluid and in fluid communication with the cavity and beingoperable to provide injection of fluid into the cavity or withdrawal offluid out of the cavity in response to a force or an impulse.

A communication channel could provide fluid communication between thereservoir and the cavity, forming a sealed system. The communicationchannel providing fluid communication between the reservoir and thecavity can be within a ring, within which the membrane and the peripheryof the rigid optical component are at least in part to provideattachment thereto.

In other embodiments, the invention could provide a variable focusoptical apparatus having two membranes attached to a periphery of saidrigid optical component to define two cavities, a variable amount offluid filling each of the cavities, and a reservoir is in fluidcommunication with at least one of the cavities.

In other embodiments, the invention could provide a set of eyeglassesfor ophthalmic applications having at least one variable focus lens, areservoir actuator and a frame, wherein the optical power of at leastone of the lenses is separately adjustable by the wearer. In certainembodiments of the eyeglasses, the reservoir could be situated in theframe and be operable by the actuator to adjust the optical power of atleast one of the lenses. In certain embodiments of the eyeglasses, thecommunication channel could be situated within said frame providingfluid communication between said reservoir and said cavity.

A liquid filled lens is capable of providing variation of optical powerover a range of up to 4.00 D.

The present invention will be better understood by reference to thefollowing detailed discussion of specific embodiments and the attachedfigures, which illustrate and exemplify such embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be understood and appreciated morefully from the following detailed description in conjunction with thefigures, which are not to scale, in which like reference numeralsindicate corresponding, analogous or similar elements, and in which:

FIG. 1A is a schematic cross-sectional view of a first embodiment of aliquid filled lens for use in spectacles or the like;

FIG. 1B is a schematic cross-sectional view of a second embodiment of aliquid filled lens for use in spectacles or the like;

FIG. 2 is an exploded schematic cross-sectional view of an embodiment ofthe spectacles apparatus utilizing the liquid filled lens;

FIGS. 3A and 3B are graphical software analyses of the performance ofthe liquid filled lens; and

FIGS. 4A and 4B are graphical software analyses of the performance ofthe liquid filled lens.

DETAILED DESCRIPTION OF THE INVENTION

The following preferred embodiments as exemplified by the drawings areillustrative of the invention and are not intended to limit theinvention as encompassed by the claims of this application.

FIG. 1A shows a cross-sectional view of a first preferred embodiment ofthe optical apparatus, in the form of a variable focus lens 10, throughwhich a wearer peers in the direction of arrow A. Lens 10 is a compositeof two optic components, an anterior (i.e., front, with respect to thewearer) optic 11 that is substantially rigid and a posterior (i.e.,back, with respect to the wearer) optic 15 that is a liquid.

Anterior optic 11 is a substantially rigid lens preferably made of arigid, transparent substrate, such as a clear plastic or poly carbonate,glass plate, transparent crystal plate, or a transparent rigid polymer,for example, Polycarbonate of Bisphenol A or CR-39 (Diethylene glycolbisallyl carbonate). Anterior optic 11 may be made of an impactresistant polymer and may have a scratch resistant coating or anantireflective coating.

In a preferred embodiment, anterior optic 11 has a meniscus shape, i.e.,convex at its front side and concave at its back side. Thus, both thefront and the back surfaces of anterior optic 11 are curved in the samedirection. However, as in all lenses that correct presbyopia (inabilityto accommodate), anterior optic 11 is thicker in the center and thinnerat the edge, i.e., the radius of curvature of the front surface ofanterior optic 11 is smaller than the radius of curvature of the backsurface of anterior optic 11, such that the respective radii ofcurvature of the front and the back surfaces of anterior optic 11, andhence the front and the back surfaces themselves, intersect. Theintersection of the front and the back surfaces of anterior optic 11 isthe circumferential edge 16 of anterior optic 11.

In certain embodiments, the front surface of anterior optic 11 isspherical, meaning it has the same curve across its entire surface, asin conventional eyeglasses lenses. In a preferred embodiment, anterioroptic 11 is aspheric and has a more complex front surface curvature thatgradually changes from the center of the lens out to the edge, so as toprovide a slimmer profile and a desired power profile as a function ofthe gaze angle, the gaze angle being defined herein as the angle formedbetween the actual line of sight and the principal axis of the lens.

Posterior optic 15 is a liquid lens composed of a fluid 14. Fluid 14 isconfined within a cavity formed between the back surface of the anterioroptic 11 and a membrane 13 that is attached to the edges of anterioroptic 11. Membrane 13 is preferably made of a flexible, transparent,water impermeable material, such as clear and elastic polyolefins,polycycloaliphatics, polyethers, polyesters, polyimides andpolyurethanes, for example, polyvinylidene chloride films, includingcommercially available films, such as those manufactured as Mylar® orSaran®. It has been found that a proprietary clear transparent film madeof Polyethylene terephthalate is one preferred choice for the membrane.

The cavity between the back surface of the anterior optic 11 and amembrane 13 in FIG. 1A is formed by sealing membrane 13 to the peripheryor circumferential edge 16 of the anterior optic 11. Membrane 13 may besealed to anterior optic 11 by any known method, such as heat sealing,adhesive sealing or laser welding. Membrane 13 can be is at least inpart bonded to a support element that is in turn bonded to the peripheryof anterior optic 11. Membrane 13 is preferably flat when sealed but maybe thermoformed to a specific curvature or spherical geometry.

Fluid 14 encapsulated between membrane 13 and the back surface of theanterior optic 11 is preferably colorless. However, fluid 14 can betinted, depending on the application, such as if the intendedapplication is for sunglasses. Fluid 14 having an appropriate index ofrefraction and viscosity suitable for use in fluid filled lenses, suchas, for example, degassed water, mineral oil, glycerin and siliconeproducts, among others that are commonly known or used for fluid filledlenses. One preferred fluid 14 is manufactured by Dow Corning® under thename 704 diffusion pump oil, also generally referred to as silicone oil.

In certain embodiments, membrane 13 by itself has no constraints in itsoptical properties. In other embodiments, membrane 13 has constraints inits optical properties, e.g., an index of refraction, that matches theoptical properties of fluid 14.

In use, at least one lens 10 is fit within a set of eyeglass orspectacle frames for use by a wearer. As shown in FIG. 1A, in profile,lens 10 allows the user to see through both anterior optic 11 andposterior optic 15, which together provide a thicker profile at thecenter of lens 10, and stronger presbyopic visual correction, than justanterior optic 11. The wearer is provided with the ability to adjust theamount of fluid 14 within posterior optic 15 and thereby adjust therefractive power of lens 10. In certain embodiments, as will bediscussed below, the frame is equipped with a reservoir of excess fluid14 and a fluid line communicating the reservoir to the posterior optic15 of lens 10. The spectacles frame also preferably has an adjustmentmechanism to allow the wearer to personally adjust the amount of fluid14 within posterior optic 15 so that fluid 14 that can be moved into orexpelled from the reservoir into the posterior optic 15 to therebyadjust the refractive power of lens 10 as needed.

FIG. 1B shows a cross-sectional view of a second preferred embodiment ofthe optical apparatus, in the form of a variable focus lens 20, throughwhich a wearer gazes in the direction of arrow A. As opposed to lens 10in FIG. 1A, which is a composite of two optic components, lens 20 inFIG. 1B is a composite of three optic components, namely, an anterioroptic 21 that is substantially rigid, an intermediate optic 25 that is aliquid and a posterior optic 35 that is a liquid.

Anterior optic 21 is a substantially rigid lens, similar in structureand design to that of anterior optic 11 of the embodiment shown in FIG.1A. As in anterior optic 11 of FIG. 1A, anterior optic 21 also has ameniscus shape, i.e., both the front and the back surfaces of anterioroptic 11 are curved in the same direction, and the radius of curvatureof the front surface of anterior optic 21 is smaller than the radius ofcurvature of the back surface of anterior optic 21, such that theintersection of the front and the back surfaces of anterior optic 21 isthe circumferential edge 26 of anterior optic 21. However, the radius ofcurvature of the back surface of anterior optic 21 is larger than theradius of curvature of the back surface of anterior optic 11 of FIG. 1A.Similarly, as compared to anterior optic 11 of FIG. 1A, anterior optic21 may be somewhat thinner than anterior optic 11 of FIG. 1A, so as tomaintain the same general overall thickness of lens 20 as compared tolens 10 of FIG. 1A.

Intermediate optic 25 is a liquid lens composed of a fluid 24, similarto fluid 14 as described with respect to FIG. 1A, that is confinedwithin a cavity formed between the back surface of the anterior optic 21and a membrane 23 that is attached to the edges 26 of anterior optic 21and is similar in structure and design to that of membrane 13 of theembodiment shown in FIG. 1A. Fluid 24 has a selected refractive index(n.sub.23).

It is preferred that intermediate optic 25 also have a meniscus shape,such that both its front and back surfaces are curved in the samedirection. Naturally, the back surface of rigid anterior optic 21 may befainted with a curvature during manufacture. However, the concavecurvature of membrane 23 may be accomplished by thermoforming it to aspecific curvature or spherical geometry when it is being sealed to theedges 26 of anterior optic 21. This may be accomplished by a reducingthe pressure within the sealed cavity formed between membrane 23 and theback surface of anterior optic 21. Thus, the radius of curvature of theback surface of anterior optic 21 is smaller than the radius ofcurvature of the membrane 23, and the intersection of the back surfaceof anterior optic 21 and membrane 23 is the circumferential edge 26 ofanterior optic 21.

Posterior optic 35 is a liquid lens composed of a fluid 34, similar tofluid 14 as described with respect to FIG. 1A, that is confined within acavity formed between membrane 23 and a membrane 33. Fluid 34 has aselected refractive index (n.sub.34).

Membrane 33 has similar in structure and design to that of membrane 13described regarding the embodiment shown in FIG. 1A. Membrane 33 mayalso be attached to the edges 26 of anterior optic 21 but posterior to,or over the edges of, the attached membrane 23. Alternatively, one ormore rings, or half-rings, may be used to provide a seat for sealingmembrane 23 and membrane 33.

Membrane 33 is preferably flat when sealed but may be thermoformed to aspecific curvature or spherical geometry. In preferred embodiments, thepositive pressure within intermediate optic 25 is lower than thepositive pressure within posterior optic 35. The greater positivepressure within posterior optic 35 controls the shape of membrane 23 andthe respective refractive powers of intermediate optic 25 within thecavity between the back surface of anterior optic 21 and membrane 23 andof posterior optic 35 within the cavity between membrane 23 and membrane33.

In use, at least one lens 20 is fit within a set of eyeglass orspectacle frames designed for ophthalmic applications for use by awearer. As shown in FIG. 1B, in profile, lens 20 allows the user to seethrough all of anterior optic 21, intermediate optic 25 and posterioroptic 35, which together provide a thicker profile at the center of lens20, and stronger presbyopic visual correction, than just anterior optic21. In certain embodiments, the wearer is provided with the ability toadjust the amount of fluid 24 within intermediate optic 25 or the amountof fluid 34 within posterior optic 35, or within both, and therebyadjust the refractive power of lens 20. In certain embodiments, as willbe discussed below, the frame is equipped with a reservoir of fluid 24or a reservoir of fluid 34, or both, and a fluid line connecting therespective reservoir to the intermediate optic 25 or the posterior optic35 of lens 20. The spectacles frame also preferably has one or moreactuators or adjustment mechanisms to allow the wearer to personallyadjust the amount of fluid 24 and fluid 34 within intermediate optic 25and posterior optic 35, respectively, so that fluid 24 and fluid 34 thatcan be moved into or expelled from the respective reservoir into theintermediate optic 25 and the posterior optic 35, and thereby adjust therefractive power of lens 20 as needed.

Other embodiments of the optical apparatus having even more opticalcomponents are also possible. In addition to lens 10 in FIG. 1A, whichis a composite of one rigid optic and one liquid optic, and lens 20 inFIG. 1B, which is a composite of one rigid optic and two liquid optics,the optical apparatus can also be a composite of one rigid optic andmore than two liquid optics. Such embodiments, which are not shown here,may provide advantages to the user and may allow more refined andsophisticated ophthalmic adjustment than the embodiments described inFIGS. 1A and 1B.

Accordingly, in preferred embodiments, lens 10 or 20 may be used forapplications in eyeglasses. Preferably, the lenses 10 or 20 for the leftand the right eye are designed independently and are capable ofadjustment of each eyeglass lens separately by the wearer. In such acase, it is preferred that a separate liquid reservoir be in fluidcommunication with each lens, i.e., connected to it by its own liquidline. In its most preferred embodiment, the liquid lens assembly,comprising the liquid lens, the reservoir and said liquid togetherconstitute a sealed system, thus minimizing incursion of water orevaporation or leakage of the liquid. The fluid is driven by some forcegenerated by a user when an adjustment in power is desired, and is thusbe moved into or expelled from the respective reservoir into the fluidoptic. The mechanism of adjustment of power of the liquid lens is bymeans of liquid transfer between the cavity and a reservoir.

FIG. 2 shows an exploded schematic cross-sectional view of an embodimentof a set of eyeglasses or spectacles 1 utilizing the liquid filled lens.Spectacles 1 has a frame or support 5, within which the variable focuslens is seated. For simplicity, FIG. 2 shows only one (the left) side ofa set of spectacles having two eyeglasses, i.e., one for each eye. Inaddition, FIG. 2 shows a variable focus lens having only one fluidoptic, e.g., as in lens 10 of FIG. 1A.

Anterior optic 11 and membrane 13 are seen in the exploded view of FIG.2, and reservoir 6, which in fluid communication with the cavity formedbetween anterior optic 11 and membrane 13, is shown. For simplicity,FIG. 2 is described herein with respect to the embodiment of lens 10having one fluid optic. In other embodiments, were spectacles 1 to havemore than one fluid optic, such as in lens 20 of FIG. 1B, more than onereservoir would be required, each in fluid communication with arespective cavity.

Reservoir 6, situated in some embodiments attached to or in frame 5, hasa hollow cavity containing extra fluid 14 that can be injected into lens10. The extra fluid 14 within reservoir 6 preferably does not completelyfill reservoir 6 so as to allow fluid 14 to be expelled from lens 10into reservoir 6. Reservoir 6 has a mechanism or actuator to move fluidinto or out of expelled it from the liquid lens optic. In oneembodiment, reservoir 6 is made of a rigid material, and is fitted witha piston that is mechanically coupled to an adjustment mechanism oractuator, such as a thumb wheel, a barrel, a clamp or a lever, that maybe attached to the rim or the lens holder, or to a frame attached to thelens holder. The actuator that provides movement of fluid 14 into or outof reservoir 6 into the cavity is not shown in FIG. 2. In certainembodiments, once the optical power of lens 10 is adjusted by theactuator, the actuator may be altered to prevent further adjustment ofthe optical properties of lens 10 by the wearer.

Reservoir 6 may be connected to a hollow ring (not shown), previouslydescribed, that performs several functions. This ring, as the seat ofthe sealed flexible membrane, provides a platform of defined width andtilt to which membrane 13 is bonded. The ring may also define the fluidchannel, in the form of a hollow space inside the ring. In oneembodiment, the ring, which ring may be set within the frame or lenssupport 5, may be provided with a series of radially placed holes oropenings through which the fluid enters the liquid lens cavity. Thisseries of holes may be placed at regular angular intervals to deliverthe fluid into the cavity at a controlled rate.

In the embodiments of spectacles 1 having more than one fluid optic,such as in lens 20 of FIG. 1B, each liquid lens cavity is preferablyprovided with a unique reservoir, and each liquid lens cavity ispreferably provided with a unique ring, so that the liquid channelsremain separate for each cavity.

The optical and mechanical design of the liquid lens enables its mainfunction, to provide capability to adjust optical power over as broad arange as possible without significantly impacting cosmetic appearance,durability or image quality. A goal of the design effort is to minimizethe volume of the liquid lens, preferably by reducing its thickness. Thethickness of the liquid lens depends on the radius of curvature of theback surface of the anterior optic 11 and the diameter of the anterioroptic 11. Therefore, the curve of the back surface of the anterior optic11 needs to be as large as possible (such that the back surface of theanterior optic 11 is as flat as possible), consistent with thespecification of optical power to be provided by the anterior optic 11.The specification of the optical power of anterior optic 11 is based onthe range of optical powers for which the liquid lens is being designed.

For the range 1.0 D to 5.0 D, for example, the preferred designconfiguration is to use a front optic in the power range of −1.0 D to+0.75 D, more preferably between −0.5 D to +0.5 D, most preferably 0.0 Dwith a radius of curvature that is consistent with optical performanceand cosmetics in this range. It is known that the front curve (radius ofcurvature) of the rigid anterior optic 11 is related to the range ofvision corrections to be provided in order to achieve optimal fieldcurvature at the far point. For example, steeper curvatures are used toprovide hyperopic corrections, while flatter curves are used for myopiccorrections.

The optical principles of selection of base curves are well known (seefor example, M. Jalie, “The Principles of Ophthalmic Lenses,” 4thEdition, Chapter 18, The Association of British Dispensing Opticians,London, 1988, and I. M. Borish, “Clinical Refraction,” 3rd Edition,Chapter 26, The Professional Press, Inc., New York, 1970).

For refractive corrections in the range of 1.0 D to 5.0 D, the preferredrange of the radius of curvature of the anterior optic 11 is between 100to 700 mm depending on the refractive index of the material used tofabricate anterior optic 11, more preferably between 500 and 550 mm, thepreferred range of thickness is 0.7 to 2.5 mm, more preferably between1.0 and 1.5 mm. It is well known that spherical aberration that affectsthe effective power provided by an optic away from its center depends onthe angle of gaze and the power at the center. For a maximum gaze angleof 20 deg, an optic of 30-40 mm in diameter and for a paraxial powerrange of 1.0 D to 5.0 D, the off axis deviation in power is expected tobe about 0.25-0.50 D.

The preferred embodiment of lens 10 consists of an anterior optic 11 ofzero power, whose thickness is equal to 1.2 mm. The front surface ofanterior optic 11 is preferably aspheric, such that the power ofanterior optic 11 drops by 0.25 D continuously over a radius of 10 mm.The whole lens 10 has a power equal to 1.21 D at the center, theposterior optic 15, i.e., the liquid layer, having a thickness of 0.32mm at the center, the lens diameter of 35 mm, while the radius ofcurvature of membrane 13 is infinity, since membrane 13 is bonded flat.

The power of lens 10 increases when the pressure of the liquid 14 isincreased by injecting more liquid into the cavity from the reservoir 6.The radius of curvature of membrane 13 is 274 mm when the lens powerreaches 3.25 D. 300 microliters of fluid is required to reach the levelof positive pressure required to cause the required level of deformation(bulging) of membrane 13.

ZEMAX is a widely-used optical design program sold by Zemax DevelopmentCorporation of Bellevue, Wash. that is used for the design and analysisof optical systems. Using ZEMAX software, the inventors were able totest the performance of lens 10 at baseline as well as over 2.0 D ofincreased power. FIGS. 3A and 3B show a ZEMAX software analysis ofon-axis (FIG. 3A) and 20 degree off-axis (FIG. 3B) performance of lens10 (anterior optic 11 and posterior liquid optic 15) at baseline. FIGS.4A and 4B show a ZEMAX analysis of on-axis ((FIG. 4A) and 20 degreeoff-axis (FIG. 4B) performance of lens 10 (anterior optic 11 andposterior liquid optic 15) over 2.0 D of power enhancement. As FIGS. 3and 4 show, the optical performance is quite good both on axis and offaxis, the difference between the sagittal and the tangential power beingless than 0.1 D at a gaze angle of 20 deg.

Thus, a liquid filled lens has been provided. One skilled in the artwill appreciate that the present invention can be practiced by otherthan the described embodiments, which are presented for purposes ofillustration and not limitation, and that the invention is limited onlyby the claims that follow.

1. A variable focus optical apparatus, comprising: a rigid, curved,transparent optical component; two transparent, distensible membranesattached to a periphery of the rigid optical component to define twocavities, a first cavity between the rigid optical component and a firstmembrane and a second cavity between the first membrane and a secondmembrane; a variable amount of fluid filling each of the cavities; and areservoir containing additional fluid and in fluid communication withthe cavity, wherein the reservoir is configured to provide injection offluid into the cavity or withdrawal of fluid out of the cavity inresponse to a force or an impulse.
 2. The variable focus opticalapparatus of claim 1 further comprising: a communication channelproviding fluid communication between the reservoir and one or more ofthe cavities.
 3. The variable focus optical apparatus of claim 2 whereinthe cavities, the reservoir and the communication channel comprise asealed system.
 4. The variable focus optical apparatus of claim 1wherein the membrane is attached to the periphery of the rigid opticalcomponent at least in part by adhesive seal or laser welding.
 5. Thevariable focus optical apparatus of claim 1 wherein the membrane is atleast in part bonded to a support element that is in turn bonded to theperiphery of the rigid optical component.
 6. The variable focus opticalapparatus of claim 1 wherein the membrane is at least in part seatedwith the periphery of the rigid optical component within a ring toprovide attachment thereto.
 7. The variable focus optical apparatus ofclaim 6 wherein the ring comprises a communication channel providingfluid communication between the reservoir and one or more of thecavities.
 8. The variable focus optical apparatus of claim 1 wherein therigid optical component is curved into a meniscus shape.
 9. The variablefocus optical apparatus of claim 1 wherein the anterior surface of therigid optical component has an aspheric geometry.
 10. The variable focusoptical apparatus of claim 1 wherein the rigid optical component has anoptical power that is at or below a minimum of the power range designedto be provided by the variable focus optical apparatus.
 11. The variablefocus optical apparatus of claim 1 wherein the rigid optical componentis made of an impact resistant polymer, a scratch resistant coating, oran antireflective coating.
 12. A set of eyeglasses designed forophthalmic applications comprising: at least one variable focus opticalapparatus of claim 1; an actuator; and a frame.
 13. The set ofeyeglasses of claim 12 wherein the optical power of at least one of thelenses thereof is separately adjustable by the wearer.
 14. The set ofeyeglasses of claim 12 wherein the reservoir is situated in the frameand is operable by the actuator.
 15. The set of eyeglasses of claim 12wherein the optical power of at least one of the lenses is adjustable bythe actuator dispenser and thereafter altered to prevent furtheradjustment.
 16. The set of eyeglasses of claim 12 further comprising: acommunication channel within the frame providing fluid communicationbetween the reservoir and one or more of the cavities.